1. Field of the Invention
The present invention relates to a processing technique of sharing data stored in an image forming apparatus such as a printing apparatus or multifunctional peripheral.
2. Description of the Related Art
Recently, distributed processing technology called grid computing has become available. A system has also appeared which adopts a so-called “distributed storage technology” of sharing storage distributed at geographically separate locations using the grid computing mechanism.
Grid computing is named after the transmission line grid of an electric power company. This technique virtualizes computing resources distributed on a network and distributes processes.
A grid computing-applied system is generally comprised of at least one computer called a master node. The computing resources of other computers (nodes) which form a grid are assigned with identifiers which are called handles and are unique in the grid. The master node monitors states such as CPU occupancy and memory utilization at each node, thereby executing so-called “scheduling” to determine and select a node optimal for performing a process at a given timing, and assign a process to the node.
The contents of concrete processes in a system employing the distributed storage technology using grid computing will now be explained simply. In locating (sharing) data managed and saved at each node in a distributed storage system, each node requests a master node to generate data. The master node generates a unique handle, associates it with the requesting node, and returns the handle to the node. The node associates the returned handle with managed/saved data.
Data located in the distributed storage system is processed by the following procedures. First, a node other than the master node transmits an operation request with a designated handle to the master node. Then, the master node transfers the operation request to a handle-associated node. The associated node executes a process corresponding to the operation request.
In this manner, the grid computing system has the merit of allowing a requesting source to manipulate data designated by a handle without being aware of which node actually manages and saves the data.
In addition to the distributed storage technology using grid computing, there have been made various proposals for sharing stored data even in the field of image forming apparatuses such as a printing apparatus and multifunctional peripherals. For example, Japanese Patent Laid-Open No. 2003-256173 discloses an invention of sharing information stored in the save unit (e.g., a hard disk drive or nonvolatile memory) of an image forming apparatus.
An image forming apparatus of this type receives a print job, performs an image forming process, and sets a shared flag. A job having a shared flag is treated as a job identifiable and operable by another image forming apparatus.
Recent image forming apparatuses are often comprised of a save area (dedicated hard disk) called a “box”. The box is a save area storing data (print images) having undergone an image forming process so as to quickly print out scanned data, FAX-received data, print data transmitted from an information processing apparatus, and the like.
Among various data saved in the image forming apparatus, data (print image stored in the box) having undergone an image forming process is also sharable in addition to the above-mentioned print job. At present, the image forming apparatus can employ distributed storage technology based on grid computing to gain some of its merits.
However, the following problems arise when sharing a print image stored in the box of an image forming apparatus (saving it accessibly from another image forming apparatus) using various “data sharing” techniques as described above.
For example, an degraded image may be generated when an external image forming apparatus outputs (e.g., prints) a shared print image. This is because an image forming apparatus which stores a shared print image and an external image forming apparatus which outputs it may have different processing characteristics.
As described above, a print image stored in the box is data having undergone an image forming process in order to print it out, and is unique data corresponding to the processing characteristic of the image forming apparatus. In many cases, another image forming apparatus cannot directly use the data.
This case is highly likely to manifest in the future because of rapid changes in processible data formats along with recent technical developments in image forming apparatuses.
In sharing print images stored in the box of an image forming apparatus, it is necessary to examine an output process method for the shared print images in another image forming apparatus. For example, it is desirable to configure each image forming apparatus to determine whether it can normally output a shared print image, so as not to actually output a degraded image. With this configuration, the image forming apparatus can avoid wasteful output of degraded images, which is convenient for users.